Various hybrid and electric powertrain architectures are known for managing the input and output torques of various prime movers in hybrid vehicles, most commonly internal combustion engines and electric machines. Some electrically-variable transmissions (EVTs) provide for continuously variable speed ratios by combining features from both series and parallel hybrid power train architectures. EVTs are operable in fixed gears with a direct mechanical path between an internal combustion engine and a final drive unit, thus enabling high transmission efficiency and application of lower cost and less massive motor hardware. EVTs are also operable with the engine mechanically independent from the final drive or in various mechanical/electrical split contributions thereby enabling high-torque, continuously variable speed ratios, electrically-dominated launches, regenerative braking, and engine off idling.
Some hybrid vehicles utilize larger battery packs, adding to the vehicle weight, increasing fuel consumption and vehicle cost. These vehicles operate in an electric-only mode over a predetermined driving range, and then the engine charges the battery through one of the motor/generators when driving beyond the optimal range. A lower battery state of charge and the higher fuel consumption required in charging the battery is generally undesirable with respect to range, endurance, and durability of a hybrid vehicle. The rate of discharge of battery and engine power are calculated based on driver commanded throttle and vehicle speed